The present invention relates to a storage apparatus and a load balancing method and, for instance, can be suitably applied to a storage apparatus for controlling a load balance of physical disks.
Generally speaking, in order to yield a high I/O performance in a storage apparatus configured from a plurality of disks, it is necessary to exploit the performance of disks configuring the backend.
Here, a RAID (Redundant Arrays of Inexpensive Disks) configuration aiming to improve the reliability of data is often used for configuring the backend, and proposed is a storage apparatus capable of configuring RAID in various levels (for 20 example, refer to Article: “A Case for Redundant Arrays of Inexpensive Disks (RAID)” David A. Patterson, Garth Gibson and Randy H. Katz.
Further, as one method of realizing the load balancing of disks, when a specific logical volume set in a physical volume enters an overloaded status, proposed is a method of copying the contents of such logical volume to a logical volume set in a backup physical device, and providing both logical volumes as one virtual logical volume to a host system in order to balance the load (for example, refer to Japanese Patent Laid-Open Publication No. 2006-053601).
Here, in a RAID configuration that performs striping processing, since data is distributed to a plurality of disks, there are cases where a single process is completed by accessing a plurality of disks. Thus, a problem arises in that the load will get centered on a specific disk configuring RAID and, when the overloaded disk reaches its processing limit, such disk will become a bottleneck and cause a processing delay, and the storage apparatus performance cannot be fully exploited (this problem is hereinafter referred to as a “diskneck”).
According to the method proposed in Japanese Patent Laid-Open Publication No. 2006-053601, although it is possible to balance the load by allocating a backup physical volume disk and increasing the number of disks to handle a single logical volume, there is a problem in that the extent available to a user will decrease since a backup physical volume must be prepared.